In Java 1.7, The item held position are slanted a bit in hand. However the held position is changed and no longer slanted after 1.8, with unknown reason and nobody noticed that.
The issue isn't present in the Bedrock Edition.
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I believe this came with the introduction of item models in 14w25a?
Hi @unknown. Please do not change the Category of bug reports. This is a field that only Mojang and Moderators are allowed to change.
The persistent tilt of the item is actually a bug on Bedrock, as noted in MCPE-152487. The slight rotation of 2D items in hand was eliminated in Java Edition 1.8 and Legacy Console Edition TU49.

Can confirm

I honestly wouldn't consider this to be an "issue" considering how you are able to change item positions with a resource pack. You could easily make a resource pack with transformations that match the 1.7 held item positions with 1:1 parity.

Item holding positions have changed significantly in version 1.8, such as eating animation, fishing rod held position, regular item held position, all these changes are unintentional and not described in changelog, so I will continue considered this issue as valid report until the mojang employee take the final decision.
Can confirm